Connection structure of non-contact rotary sensor with rotating shaft

ABSTRACT

The present invention is a coupling structure to connect a rotating shaft  119  to a non-contact type rotary sensor, which comprises a first stator  111  having two magnetic facing sides  111   a,    111   b  which are disposed on a same arc and are apart from each other, a second stator  112  having one magnetic facing side  112   a  which is disposed between the two magnetic facing sides on the arc, a hall element  113  disposed between the first and the second stators, a moving magnet  114, 115  having different polarities which is disposed along the outside arc of the three magnetic facing sides, and a rotor  116  having the moving magnet, wherein a fitting hole  116   b  is formed at the rotor in which the rotating shaft is loose-fitted, the rotating shaft which is inserted to the fitting hole is supported by the fitting hole by a pin which is piercing the rotating shaft, and a clearance keeping member is disposed to keep the distance between the moving magnet and the first and the second stators constant. With this structure, a rotary sensor that can detect angles accurately even if there is misalignment between the center of the rotor and the center of the rotating shaft is provided.

TECHNICAL FIELD

[0001] The present invention relates to a coupling structure of a rotarysensor and a rotating shaft which is connected to the rotary sensor.

BACKGROUND ART

[0002] The applicant proposed a non-contact type rotary sensor whichutilizes a hall element as shown in FIG. 6, in Japanese patentapplication No. H11-255409. This rotary sensor 10 comprises a firststator 11 having two magnet facing sides 11 a, 11 b, a second stator 12having one magnet side 12 a, a hall element 13 provided between thefirst and second stators, moving magnets 14, 15, and a rotor 16 to fixthese moving magnets.

[0003] Abovementioned three magnet facing sides 11 a, 11 b, 12 a arearranged on nearly the same arc and practically form a circlealtogether. On the other hand, the moving magnets 14, 15 are curvedplate-shaped magnets which have the same curvature center of the arc atthe magnet facing sides, and have poles at the plate thicknessdirection, and are arranged along the arc so that the poles of themoving magnets that are located next to each other are opposite to eachother. The rotor 16 rotates along the arc.

[0004] In this example, when the moving magnets 14, 15 move along thearc, the magnetic flux passing through the hall element 13 changes.Therefore, by detecting the changes, the rotating angle of the rotor canbe detected. Here, because the length of the two magnet facing sides 11a, 11 b of the first stator 11 can be set appropriately, the angle rangeof usage can be obtained as desired, and the resolution can be improvedin this range.

[0005]FIG. 7 is a sectional view of the abovementioned rotary sensor inthe assembled state, and FIG. 8 is a sectional view of VIII-VIII in FIG.7. As shown in FIG. 7, the first stator 11 and the second stator 12 aredisposed in a case 17, and the hall element 13 is inserted between thestators.

[0006] The space inside the case 17 in which these are fitted is coveredby a cover 18. A center pin 18 a is disposed to the cover 18, and isfitted to a bearing hole 16 a of the rotor 16 penetrating the firststator 11.

[0007] In ordinary cases, the rotor 16 receives offset force by theattracting force of the moving magnets 14, 15 to make the moving magnets14, 15 get closer to the first and the second stators. However, theoperation accuracy is maintained and the rotor 16 can rotate smoothly,because the center pin 18 a is fitted to the bearing hole 16 a of therotor 16, and the slight clearance between the center pin and thebearing hole is offset. Further, in case the rotor 16 is shifted to thedirection of the length of the center pin 18 a, it is attracted to acertain position by the attracting force between the moving magnets 14,15 and the first and the second stators 11, 12. Based on the descriptionabove, the rotary sensor of this type is impervious to being swung byvibration, and as a result, has an advantage of not producing outputfluctuations.

[0008] A hole 16 b is formed at the opposite side of the rotor 16 towhich a rotating shaft 19 as a counterpart is fitted. As shown in FIG.8, a cut portion 19 a, which is called D-cut from its sectional shape,is formed at the top end of the rotating shaft 19. In addition, the hole16 b has the same shape as the D-cut portion 19 a of the rotating shaft.Therefore, when the D-cut portion 19 a is fitted to the hole 16 b, therotation of one can be transferred to the other.

[0009] When the abovementioned rotating shaft 19 and the hole 16 b ofthe rotor are fitted together, it is ideal that the axes of both of themare perfectly aligned. However, it is actually normal that there is somemisalignment because of the variation of accuracy at the time ofproduction.

[0010] Therefore, the rotor 16 is inclined being affected by themisalignment, and the distance T′ between moving magnets 14, 15 and thefirst and the second stators 11, 12 which is shown in FIG. 7 isfluctuated, and the detecting accuracy of the non-contact type rotarysensor 10 is greatly affected.

[0011] The present invention was devised in the light of theabovementioned facts, and it is an object to provide a rotary sensorwhich can detect accurate angles even if there is some misalignmentbetween the center of the rotor and the center of the rotating shaft.

[0012] Disclosure of the Invention

[0013] To achieve the abovementioned object, the present inventionadopts a coupling structure to connect a non-contact type rotary sensorand a rotating shaft which comprises a first stator having two magneticfacing sides which are disposed on a same arc and are apart from eachother, a second stator having one magnetic facing side which is disposedbetween the two magnetic facing sides on the arc, a hall elementdisposed between the first and the second stators, a moving magnethaving different polarities which is disposed along the outside arc ofthe three magnetic facing sides, and a rotor having the moving magnet,wherein a fitting hole is formed at the rotor in which the rotatingshaft is loose-fitted, the rotating shaft is inserted to the fittinghole and is pierced by a pin so as to have contact with the rotor and tobe supported being free to swing, and a clearance keeping member isdisposed to keep the distance between the moving magnet and the firstand the second stators constant. It is possible to adopt a structure ofa steel ball as the clearance keeping member.

[0014] It is possible to adopt a structure wherein the width of thefirst stator and second stator is wider than the width of the movingmagnet in the direction of the rotating shaft, the moving magnet alwaysstays within the range of the width of the first stator and the secondstator in the rotating range of the rotor, and the angle between thecenter line of the pin and the normal line of the rotating shaft at theinitial position is within ±45°. It is also possible to adopt astructure that the center line of the pin overlaps the normal line.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015]FIG. 1 is a view showing an embodiment of a coupling structure ofa non-contact type rotary sensor and a rotating shaft of the presentinvention; (a) is a sectional view of the main part, and (b) is a leftside view of the facing part of a rotor and a stator.

[0016]FIG. 2 is a sectional view of II-II in FIG. 1 (a).

[0017]FIG. 3 is a sectional view of the main part of an embodiment whichdoes not adopt a ball as a clearance keeping member.

[0018]FIG. 4 is a side view showing the state that a non-contact typerotary sensor and an acceleration pedal of the present invention iscoupled.

[0019]FIG. 5 is a diagram showing the relationship between offsetamounts of a rotating shaft and output fluctuation values of the sensor.

[0020]FIG. 6 is a view showing a structure of a conventional non-contacttype rotary sensor.

[0021]FIG. 7 is a sectional view showing an assembling state of a rotarysensor of FIG. 6.

[0022]FIG. 8 is a sectional view of VIII-VIII in FIG. 7.

BEST MODE FOR CARRYING OUT THE INVENTION

[0023] An embodiment of the present invention is explained preciselywith reference to the drawings.

[0024]FIG. 1 (a) is a sectional view showing an embodiment of a couplingstructure of a rotary sensor and a rotating shaft of the presentinvention, and (b) is a side view of a facing part of a rotor and astator, viewing from the left side of (a). FIG. 2 is a sectional view ofII-II in FIG. 1 (a).

[0025] As shown in these figures, the first stator 111 and the secondstator 112 are fitted at specific positions of a body 117 of the rotarysensor 110. Two magnetic facing sides 111 a, 111 b of the first stator111 which are disposed being apart from each other, and one magneticfacing side 112 a of the second stator 112 which is disposed betweenthem are lined on the same arc. Although three magnetic facing sides 11a, 11 b, 12 a of the conventional example practically form a circle,those of this embodiment form about one-third of a circle. Two hallelements 113, 113 are disposed between the first stator 111 and thesecond stator 112, and a terminal 113 a of the hall element 113 isconnected to a terminal 101 of a connector, not shown in the figures, bysoldering or the like.

[0026] A rotor 116 integrally connects a stator facing portion 116 awhich curvature center is the same as that of the arc formed by thethree magnetic facing sides, and a supporting portion 116 c which has ahole 116 b that is fitted with the rotating shaft 119. There is noclearance at the diameter of the hole 116 b in the direction that a pin102 is fitted, and the diameter of the hole 116 b is larger than thediameter of the rotating shaft 119 in the direction which isperpendicular to the pin 102. The pin 102 is fitted to the rotatingshaft 119 and the supporting portion 116 c of the rotor 116, so as toprevent them from dislodging. A spring pin is used as the pin 102 toprevent looseness. As structured as abovementioned, the rotor 116 canrotate together with the rotating shaft 119, and can swing with the pin102 being the center without misaligning in the direction of the pin102.

[0027] As same as the conventional example, moving magnets 114, 115which are consisted of two plate-shaped magnets are disposed at thestator facing portion 116 a. Outside of these, a steel-made ball isinserted as a clearance keeping member to keep the clearance between themoving magnet 114, 115 and the first stator and the second stator 111,112.

[0028] Although the rotor 116 is attracted towards the first stator andthe second stator 111, 112 by the attracting force of the moving magnets114, 115, the ball 103 prevents them from sticking together, so that theclearance T can be kept constant. Furthermore, because the ball 103 ismade of steel, it is attracted towards the moving magnets 114, 115 sothat the position in the thrust direction of the rotating shaft 119 isconstantly stable.

[0029] Next, the operation in case there is some misalignment betweenthe center of the rotor 116 and the center of the rotating shaft 119 dueto the variation of dimensional accuracy is explained. Because thisrotary sensor 110 is the type to detect rotating angles by the changesof magnetic flux, when the distance T between the moving magnets 114,115 and the first stator 111 or the second stator 112 varies, themagnetic flux to the hall element varies so that the output fluctuationsare produced.

[0030] However, with the structure of the embodiment of the presentinvention, even if there is some misalignment between the center of therotating shaft and the rotor, the distance T between the moving magnets114, 115 and the first and the second stator 111, 112 are determined bythe ball 103, and the misalignment is absorbed by the swing of the rotor116. On the other hand, the rotor 116 and the rotating shaft 119 areconnected by the pin 102, and the connection produces no looseness atall in the rotating direction. Therefore, the rotating angle of therotating shaft 119 can be detected accurately. Especially, when the ball103 is made of steel, because it is attracted towards the moving magnets114, 115 by magnetic force, the position in the rotating shaft 119direction becomes stable. Then, the fluctuation of the distance Tbecomes smaller.

[0031] Furthermore, even if some misalignment occurs due to dimensionalaccuracy or wears by operation or the like at the center of the bearingto the rotating shaft 119, the rotor 116 is not strained. Therefore,high durability of the rotor is obtained.

[0032]FIG. 3 shows an embodiment which does not adopt a ball, and is aview showing the vicinity of a stator facing portion 126 a of a rotor126. As shown, a projection 126 b can be used instead of a ball 103 as aclearance keeping member. In this structure, the cost is reduced in theview that the rotor can be formed of resin or the like integrally.

[0033] As shown in FIG. 4, an acceleration pedal 104 is connected to therotating shaft 119 of the non-contact type rotary sensor 110 of thepresent invention. Namely, the rotary sensor 110 of this embodiment isused to detect the depressing amount of the acceleration pedal.

[0034] The rotating angle range of the acceleration pedal 104 isrelatively small, approximately 10° through 20°. Then, because therotating movement is repeated within the narrow rotating range, thecontacting portions between the rotating shaft 119 and the hole 116 b ofthe rotor receive intensive contacting force and are worn lopsidedly.

[0035] Here, each axis of x, y, z is defined as shown in FIG. 1 (b). Thedirection of the length of the pin 102 is x axis, and the direction ofthe diameter of the rotating shaft 119, which is perpendicular to xaxis, is y axis. Then, when the relationship between offset amounts dueto the wear and output fluctuation values is examined, the diagram shownin FIG. 5 is obtained. In this figure, a solid line shows the outputchanges to the offset amounts in x axis, and a dotted line shows thoseto the offset amounts in y axis respectively. It is found that the wearin y axis direction is more sensitive to the output of the rotary sensorthan that in x-axis direction. On the contrary, even if the wear occursin z axis direction, the misalignment in z axis direction does not causeany output change, as long as the width b of the first and the secondstator 111, 112 in FIG. 1 (a) is wider than the width B of the movingmagnets 114, 115, and the width B of the moving magnets 114, 115 iswithin the range of the width b of the first and the second stator 111,112 during an operating state.

[0036] Therefore, in the embodiment of the present invention, the pin102 is disposed along the direction to which the wear due to theoperation occurs.

[0037] It is explained more specifically with reference to FIG. 4. InFIG. 4, a line 51 shows the position where the acceleration pedal 104 isat an idling state, namely, the initial position of the rotating shaft.A line 52 shows the position where the acceleration pedal is at a fullthrottle state, shown as 104′. A line 54 is a normal line to the line51. When the acceleration pedal 104 is pressed and depressed repeatedlybetween the line 51 and the line 52, which is the rotating range, thewear occurs at the bearing hole of the rotating shaft in the directionof the normal line 54. Therefore, the pin 102 is arranged so that thenormal line 54 is aligned to the center line of the pin 102 (X axis).Even in case when it is impossible to set to be perpendicular, settingthe angle β, which is the angle between the center line 55 of the pin102 and the normal line 54, within ±45° is still effective, and settingit within ±30° is the desired range because of high effectiveness.

[0038] To utilize the structure of this embodiment, firstly, therotating shaft 119 is attached to the rotor 116 being free to swing bythe pin 102. Next, the rotating shaft 119 is assembled with theacceleration pedal 104 so that the pin 102 is perpendicular to the line51 of the initial position of the acceleration pedal 104, or within ±45°(more desirably ±30°).

[0039] In addition, although two magnets are used in the presentinvention, not limiting to this, it is also possible to use one magnetwhich has different polarities.

[0040] Industrial Applicability

[0041] According to the present invention, in a coupling structure toconnect a non-contact type rotary sensor and a rotating shaft, a fittinghole is formed at the rotor in which the rotating shaft is loose-fitted,the rotating shaft is supported by a pin which is piercing the rotatingshaft, and a clearance keeping member is disposed to keep the distancebetween the moving magnet and the first and the second stators constant.Therefore, even in case that misalignment between the rotating shaft andthe center of the rotor occurs, or in case that some looseness isproduced due to the wear at the bearing of the rotating shaft, thelooseness is absorbed by the swing movement of the rotor being the pinas the center, and the distance between the moving magnet and the firstand second stators are kept constant by the clearance keeping member, sothat accurate detection of the angle is possible.

[0042] When a steel ball is used as the clearance keeping member, thewear during the rotation of the rotor is degreased so that thedurability is improved. Furthermore, because steel is a magneticmaterial, it is attracted towards the moving magnet and the position ofthe steel ball becomes stable. Then, the detecting accuracy can befurther improved.

[0043] When the structure wherein the width of the first stator andsecond stator is wider than the width of the moving magnet in thedirection of the rotating shaft, the moving magnet always stays withinthe range of the width of the first stator and the second stator in therotating range of the rotor, and the angle between the center line ofthe pin and the normal line of the initial position of the rotatingshaft is within ±45° is adopted, even if the lopsided wear is producedat the rotating shaft due to the small range of the rotation, thedegradation of accuracy of the angle detection can be minimized.

1. A coupling structure to connect a non-contact type rotary sensor anda rotating shaft, comprising: a first stator having two magnetic facingsides which are disposed on a same arc and are apart from each other; asecond stator having one magnetic facing side which is disposed betweensaid two magnetic facing sides on said arc; a hall element disposedbetween said first and said second stators; a moving magnet havingdifferent polarities which is disposed along the outside arc of saidthree magnetic facing sides; and a rotor having said moving magnet;wherein a fitting hole is formed at said rotor in which said rotatingshaft is loose-fitted; said rotating shaft is inserted to said fittinghole and is pierced by a pin, so as to have contact with said rotor andto be supported being free to swing; and a clearance keeping member isdisposed to keep the distance between said moving magnet and said firstand said second stators constant.
 2. The coupling structure of anon-contact type rotary sensor and a rotating shaft according to claim1, wherein said clearance keeping member is a steel ball.
 3. Thecoupling structure of a non-contact type rotary sensor and a rotatingshaft according to claim 1 or claim 2, wherein the width of said firststator and second stator is wider than the width of said moving magnetin the direction of said rotating shaft; said moving magnet always stayswithin the range of said width of said first stator and said secondstator in the rotating range of said rotor; and the angle between thecenter line of said pin and the normal line of said rotating shaft atthe initial position is within ±45°.